A high-performance liquid chromatographic assay developed in this laboratory was used to study the stability of spiromustine in its infusion vehicle, 10% fat emulsion (intralipid). The findings indicated 10% loss in 16 minutes, a much more rapid drug degradation than was previously postulated. Formulation and drug administration data on spiromustine have also been updated in the current issue of "NCI Investigational Drugs: pharmaceutical data, 1985". The HPLC-EC method used for drug stability studies was evaluated for sensitivity and linearity and found to be suitable for following plasma concentration-time profile of the drug after single doses.